The on-resistance of a typical high voltage power metal-oxide semiconductor field effect transistor (MOSFET) is dominated by the resistance of the voltage sustaining drift zone. The blocking voltage capability of the drift zone is typically based on its thickness and doping. To increase the blocking voltage, the doping of the drift zone is typically reduced and the layer thickness is increased. The on-resistance of the typical transistor therefore increases disproportionately strongly as a function of its blocking voltage capability. For a 600V transistor, for example, the drift zone contributes over 95% of the total on-resistance. Thus, to improve the performance of power MOSFETs, the drift region resistance should be reduced.
For these and other reasons, there is a need for the present invention.